Latest Poll: Yes On 8 Down By 5

Over the past six weeks, a proposed constitutional amendment that would end same-sex marriage in California has gained substantial ground but still trails by a five-point margin heading into Tuesday's election.

A new Field Poll shows Proposition 8, one of the most closely watched state ballot measures in years, is supported by 44 percent of likely voters. Forty-nine percent oppose it, and 7 percent are undecided.

In the last Field Poll, released Sept. 18, the measure was behind by 17 points.

"It's certainly closer than it was before the advertising campaign hit," said Field Poll director Mark DiCamillo. "A lot of that has to do with the campaigning on the Yes (on 8) side."

The battle for Prop 8 is now the most expensive social referendum fight ever waged, and is the second-most expensive campaign this year behind the presidential race.

According to outside estimates, the campaigns for and against Proposition 8 have raised more than $60 million in donations, setting a new record nationally for a social policy initiative—and trumping every other race in the country this year in spending except the presidential contest.

By comparison, the second-highest campaign spending numbers in the country can be found in Minnesota's Senate race between the Republican incumbent Norm Coleman and comedian Al Franken, where the sides have raised about $35 million combined. Similar initiatives to ban same-sex marriage in Arizona and Florida have raised just over $11 million combined.